5.4 Engine loses power on acceleration.

[BOB4254]

1998 Expedition XLT 5.4L. 125K miles. Bought new in 1998. Oil & filter change every 3-5K miles. Trans Oil & filter change every 30-35K miles since new.

Within the last 12 months new fuel pump & fuel filter & air filter. Cleaned & tested fuel injectors. New plugs & coils.

Installed new Throttle Position Sensor.

Cleaned Map sensor & Throttle Body. Removed any slack from throttle cable.

No vacuum leaks detected.

No trouble codes.

Idles so smooth & quite your not sure if the engine is running.

Normal lite acceleration shifts 1-2-3-4 perfectly and smooth. At 45 mph press gas pedal a little more she goes into passing gear.


Recent Issue: When at approx 45mph and press gas pedal to the floor to go into passing gear, engine bogs down & stays at 2000 rpm.

OR

When accelerating from zero, and press gas pedal to the floor engine bogs down.

Has this happened to any of my fellow Expedition owners?

Any advice on the possible cause & fix?

Thanks for your help, Bob

 

[Eric in Wyoming]

That throttle position sensor might need calibrated, and I have no clue how to do it if that's the case. Also could have an issue with your MAP sensor. Sounds like when you hammer down on it the ECM isn't picking up the vacuum drop. Did you clean the MAP sensor or the MAF sensor - the one just downstream of the air filter is the MAF sensor.

 

[BOB4254]

Installed new Throttle Position Sensor. Cleaned Map & MAF sensors & Throttle Body. TBS does not seen to have any adjustments for
calibration?

 

[Agktown162]

Is it hot where you live?

do you have a cai?

AC on or off?

 

[BOB4254]

Is it hot where you live? YES
do you have a cai? WHAT IS CAI?
AC on or off? YES TO BOTH